The primary objective of this study is to determine the annual and lifetime criminality of narcotic addicts in U.S. cities. Both annual and lifetime measures of criminal behavior (expressed as crime-days per year at risk) have been employed in the investigators' past research to explore the interrelationships of addiction and crime. In the present study, four crime-days measures will be derived on the basis of new data collected in three cities. The research design involves the collection of comprehensive data on the criminal behavior of 350 narcotic addicts in The Bronx (New York), Philadelphia, and Baltimore. A sample of 150 male addicts from the first of these cities and 100 each from the second and third will be obtained from consecutive admissions to methadone maintenance treatment programs. Four crime-days measures of criminality will be employed: CD-I Theft, CD-II Violence, CD-III Drug Dealing, and CD-IV Other Crime. These 350 addicts will be interviewed by a specially trained staff utilizing a shortened version of an interview schedule already validated in work with over 400 addict subjects. As to national significance, the results of this study should materially expand current knowledge concerning the impact of narcotic (principally heroin) addiction upon crime in the U.S. Moreover, it will provide up-to-date information as to whether the extent of addict criminality found to obtain in Baltimore (in 1973 and before) applies to other U.S. cities in 1983 as well. This issue is of considerable consequence inasmuch as addicts in the earlier, probability-based Baltimore sample committed over 2,000 offenses per individual during an 11 year risk period, and current estimates fix the narcotic addict population in the U.S. at 450,000.